A double-aerosol device is known which has a double container structure formed of an inner container storing contents and an outer container storing the inner container, and has a structure to discharge the contents to the outside by a pressure of propellant filled in a space between the outer container and the inner container. As the double-aerosol device of such a type, a duplex can container is widely used, in which two aerosol containers respectively store one inner bag (inner container) in one can (outer container) and are arranged in parallel, a first agent such as hair dye is stored in one inner bag and a second agent is stored in the other inner bag.
Meanwhile, a double-aerosol device that is configured such that two inner containers are stored in one outer container is also proposed (see PTL 1). Specifically, in order to grasp a remaining amount of contents based on a degree of deformation of the inner container, the double-aerosol device configured to store two inner bags (inner containers) formed in a tuck-folded pleat shape in a transparent outer container is disclosed in PTL 1.